Sports Nutrition Basics - Marlington Local



Sports Nutrition Basics

Part 1 - Carbohydrate

All energy, whether it's to play sport or carry out any other activity, comes from three classes of food called macronutrients. These nutrients are better known as carbohydrates, fats and proteins. Each is important - not only to fuel athletic performance but also for overall health and well-being.

Weight for weight carbohydrates contain the least amount of energy out of the three macronutrients. Yet they are the most important type of fuel to an athlete.

During short, intense bouts of exercise (like sprinting), carbohydrate is the only fuel capable of supplying the body with energy quickly enough. In the first few minutes of any activity, it is carbohydrate that almost exclusively meets energy demands. In addition, the ability to repeat a sprint at the end of a game or race, to the same high level as at the start of the game relies, in part, on the body's carbohydrate stores.

Although the body does use fat for lower intensity activity, carbohydrate acts as a "primer" or catalyst for fat to be broken down. Finally, carbohydrates play a key role in central nervous system function. The brain for example, uses glucose almost exclusively as its fuel.

Can diet significantly affect the body's carbohydrate stores?

The average person has about 2000 calories of stored carbohydrate. An overnight fast (8 to 12hrs) and a low-carbohydrate diet can dramatically lower these stores. More importantly, a carbohydrate-rich diet can more than double them. The body's upper limit for carbohydrate storage equates to about 15 grams per kilogram (2.2lbs) of bodyweight. So an 80kg (175lb) person can potentially store up to 1200 grams of carbohydrate or 4800 calories worth of energy - all with just a few dietary modifications.

There are different types of carbohydrates. Understanding what they are and how they affect the body differently, is important to athletes and what they eat before and after a game.

Monosaccharides

This is the most basic unit of carbohydrate. Examples of monosaccharides include fructose (sugar found in fruit) and glucose (also called blood sugar). Cells can use the glucose found in food directly for energy, while fructose is converted to glucose in the liver.

Disaccharides

Combine two monosaccharides and the result is a disaccharide. Sucrose or table sugar is a disaccharide and it's the result of combining glucose and fructose. The sugar in milk, lactose, is another disaccharide. The collective name for both monosaccharides and disaccharides is simple sugars. Simple sugars are quickly absorbed by the body and provide a rapid source of energy.

Simple sugars such as fruit and energy drinks are a good food choice to refuel AFTER a game when the body's energy stores are low.

Polysaccharides

Starch and fibre are both polysaccharides. Starch is the combination of hundreds of monosaccharides joining together. Nutritionists often refer to polysaccharides as complex carbohydrates. Examples include bread, potatoes, rice and pasta. It takes longer for the body to break these complex structures down so they release their energy over a longer period than simple sugars.

Fiber differs from starch in that it cannot be digested and used for energy. It's still an important dietary component though and there is a growing link between lack of fibre and certain degenerative illnesses.

Starchy complex carbohydrates are the best choice BEFORE a game as a pre-match meal.

In Part 5 of this series, we'll cover sample pre and post competition meals and what they should contain. Closely related to the subject of carbohydrates is the Glycemic Index and that's something we'll cover later also.

Sports Nutrition Basics

Part 2 - Fat

Fat contains more than twice the amount of energy as carbohydrate. A single gram contains nine calories making it a valuable source of fuel for longer duration activities. While fat cannot supply energy quickly enough for very intense activity, it can be used by the body to power lower intensity exercise such as jogging and walking.

Fat also provides insulation and protection to vital organs such as the heart, lungs and liver and transports vitamins throughout the body.

Not all dietary fat is the same. Like carbohydrate, fat can be broken down into several different groups:

Saturated Fats

Saturated fats are found in foods such as red meat, egg yolks, cheese, butter, milk and commercially prepared cakes, pies and cookies. The typical western diet consists of almost 40% total fat. Of this, 15% is made up of saturated fats, which is considered a major cause of coronary heart disease, diabetes and other degenerative illnesses. No more than 10% of the diet should come from saturated fats.

Unsaturated Fats

Unsaturated fats come in the form of monounsaturated fats and polyunsaturated fats. Monounsaturated fats can actually lower the risk of coronary heart disease and are found in foods like olive oil, canola oil, avocados, almonds and pecans. Polyunsaturated fats, found in sunflower oil, safflower oil and corn oil are not thought to contribute to heart disease but don't offer the same protection as monounsaturated fats.

Essential Fatty Acids

Essential fatty acids are a class of polyunsaturated fats that have received a lot of attention in the media recently. They are thought to be cardio-protective and may help prevent a range of other illnesses. There are three types of essential fatty acids - Omega 3, Omega 6 and Omega 9. Omega 3 and Omega 6 must be consumed while the body can produce some Omega 9 on its own. Essential fatty acids are required for healthy cardiovascular, reproductive, immune, and nervous systems. Found in foods like walnuts, pumpkin seeds, Brazil nuts, sesame seeds, avocados, some dark leafy green vegetables and oily fish, the typical Western diet is often deficient of essential fatty acids.

Cholesterol

Despite its bad press, cholesterol is actually essential for many important bodily functions. There are essentially two types of cholesterol - low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL is known as the "bad" cholesterol because it carries and then deposits cholesterol at the artery walls. HDL on the other hand, is known as "good" cholesterol because it acts as a scavenger removing cholesterol from artery walls and transporting it to the liver to be excreted.

Although some foods like cream, butter, ice cream, egg yolks, shellfish and red meats contain cholesterol, it's a high intake of saturated fat that causes the body to synthesize too much cholesterol. The maximum amount of dietary cholesterol recommended each day is 300mg.

Sports Nutrition Basics

Part 3 - Protein

Correct and adequate protein intake is crucial for anyone involved in vigorous training. Protein is essential for the growth and repair of skin, hair, nails, bones, tendons, ligaments and muscles. It also serves a crucial role in enzyme production and maintaining a strict acid-base balance.

The Recommended Dietary Allowance (RDA) for the average male and female adult is just 0.83 grams of protein per kilogram (2.2lbs) of bodyweight. In a 70kg (154lb) individual this equates to just 58 grams of protein per day or about two chicken breasts worth.

Some research shows that competitive athletes, particularly those involved in heavy weight training, may require more protein. The recommendation for strength and endurance athletes ranges from 1.2 to a maximum of 2.0 grams per kilogram (1kg = 2.2lbs). Research has shown that consuming more protein than this serves no benefit and may be harmful in the long term.

Good sources of protein include low fat milk, poultry, fish, lean red meat, eggs, nuts, beans and lentils and soy products. Fatty meats like pork and fast food hamburgers as well as most cheeses contain a lot of saturated fats so are not as suitable sources of protein.

Recently, the emergence of high protein, low carbohydrate diets have become popular in the weight loss industry. While they may or may not help to shed the pounds, high protein, low carbohydrate diets are unsuitable for athletes.

Many athletes are afraid that their heavy training schedule will force their bodies to breakdown lean muscle mass and then use it as energy. The body does use protein sparingly as a source of fuel after 45 minutes of exercise, however consuming more protein is not a good strategy.

By consuming plenty of carbohydrates before, during and after exercise it acts as a protein "sparer". Only in the absence of adequate carbohydrate stores will the body begin to metabolise significant amounts of protein for use as energy.

The Athlete's Diet

A typical western diet contains too much fat and not enough healthy, whole grain carbohydrates.

Athletes should aim to make 60-65% of their diet carbohydrate, with an emphasis on fresh fruit and whole grains such as brown rice and pasta, wholemeal bread, potatoes and high fibre cereals. About 20-25% of total calories should be in the form of fat.

The majority of this should be in the form of good fats (monounsaturated, polyunsaturated, omega fatty acids) found in oily fish like mackerel and salmon, olive oil, avocado and raw nuts (not roasted or salted). Protein should make up the remaining 10-15% of an athlete's diet derived from fish, poultry, low fat milk and lean red meat for example.

Ideal Diet composition for a Sport Player

Carbohydrate Fat Protein

Average Western Diet 46% 38% 16%

Ideal Sport Player’s Diet 60% 25% 15%

Take a look at the table below for a sample day's eating plan:

Sample Day’s Diet for a Sport Player in Training

Breakfast Piece of fruit Bowl of oatmeal or porridge (sweeten with dried fruit or honey) 3-4 slices whole meal bread toasted with small amount of butter/olive oil spread, jelly/jam Glass of fresh fruit juice (not concentrated)

Snack Piece of fresh fruit Plain yogurt 2-3 fig biscuits/cookies

Lunch Tuna or grilled chicken Bagel, baguette etc. (preferable wholemeal) Mixed salad with olive oil and lemon juice dressing Glass fresh fruit juice or low fat milk Low fat or bran muffin 1-2 bananas

Snack Bag of nuts and raisins (such as almonds, pecans Hazelnuts etc)

Dinner Large serving rice or pasta Tomato sauce Grilled fish, chicken or lean beef mince Large mixed vegetable salad with dressing Small serving of ice cream and strawberries

Sports Nutrition Basics

Part 4 - Vitamins & Minerals

Thirteen different vitamins have been identified and studied to date. They are classed as either fat-soluble (vitamins A, D, E, K) or water-soluble (vitamin B complex, vitamin C). Together they are responsible for blood clotting, neuromuscular function, healthy skin, teeth and bones and numerous other bodily functions.

A well-balanced diet should provide an adequate supply of all the vitamins regardless of age and level of physical activity. During periods of intense training, a natural increase in food intake supplies any extra vitamin demand the body may have.

Free Radicals, Antioxidants & Exercise

Free radicals are highly reactive molecules that can cause damage to the cells and are thought to accelerate the aging process and contribute to cancer, heart disease and diabetes. They are found in cigarette smoke, environmental pollution and some medications. Exercise may also increase the production of free radicals.

The body has an elaborate defense system against free radicals in the form of antioxidant enzymes. Vitamins A, C and E are known as antioxidant vitamins and can protect the cells against free radical damage. Although foods like citrus fruits, green vegetables and nuts contain antioxidant vitamins, some athletes feel the need to take a supplement due to the high level of training they undergo.

Although exercise is thought to increase free radical production, it also appears to increase the body's antioxidant defense system at the same time. However, there is some research to suggest that a vitamin E supplement can reduce harmful free radical production associated with exercise. Whether this offers any overall health benefits is still unclear.

Over 40 years of research has failed to show that vitamin supplementation can offer any sort of performance enhancement when a nutritionally balanced diet is present. Some vitamins (such as vitamin C) taken in excess can actually be harmful. The recommendation is to eat a well balanced diet rich in fresh fruit and vegetables.

Minerals

Minerals account for roughly 4% of a person's body mass. They provide the structure for forming bone and teeth. They also help muscles to contract, maintain normal heart rhythm and control the acid-base balance as well as other important bodily functions.

Minerals are classed as either major or trace depending on how much is required per day. Major minerals include calcium, phosphorus, sodium, potassium and magnesium. Trace minerals include iron, zinc, copper, selenium and chromium.

Calcium

The typical Western diet contains too little calcium. The RDA for calcium is 800-1000 mg for adults and 1200 mg for adolescents. The average adult consumes just 500-700 mg per day and for many it's as little as 300 mg per day. Calcium deficiency can lead to a condition called osteoporosis - a weakening of the bones. Exercise actually helps to maintain healthy bone density.

Sodium

Most adults consume too much sodium (found in abundance in processed foods), which can lead to high blood pressure. The RDA of 1100-3300 mg is equivalent to 0.5-1.5 teaspoons of table salt. Most people consume more than 2 teaspoons from processed foods even when table salt isn't used as seasoning.

Iron

Iron is helps the blood to carry oxygen so an iron deficiency (called anaemia) can lead to fatigue even with mild exercise. Some research has suggested that heavy exercise training creates an increased demand for iron. However, even in elite athletes, supplements are unnecessary if the diet contains iron-rich foods.

As with vitamins there is no convincing research to suggest taking mineral supplements can improve sporting performance. Exceeding the recommended daily allowance can also be potentially harmful.

Sports Nutrition Basics

Part 5 - Pre & Post Competition Eating

Long gone are the days when athletes thought that eating a big steak before a game would give them lots of energy. Today's elite sports men and women follow a strict diet, particularly on the day of a competitive match or event. While diet won't turn poor athletes into great ones, it can make the difference between performing poorly and tapping your full potential.

The Glycemic Index

Not all carbohydrate is digested and absorbed at the same rate. The Glycemic Index (GI) is a scale of how much a particular type of food raises blood sugar over a two-hour period compared to pure glucose.

For example, a piece of food with a GI score of 45 means that it raises blood sugar 45% as much as pure glucose in that two-hour period.

Common sense says that simple sugars which are broken down quickly, like fructose in fruit, should have a higher GI than complex carbohydrates, but that's not always the case. White bread, white rice and potatoes (all classed as complex carbohydarets) have a very high GI. That means they raise blood sugar almost as much or even more than pure glucose. Fructose has medium GI because the fibre found in fruit slows digestion and absorption.

Choosing foods with a high GI will help to quickly replenish carbohydrate stores after a game or event. Before a game or event, low GI foods are more appropriate as they release energy more slowly and for a longer period.

Pre Match Eating

The goal prior to a game or event (and even a training session) is to maximise carbohydrate stores in the muscles and liver and to top up blood glucose stores. Studies have shown that consuming foods with a high GI within an hour of exercise can actually lower blood glucose, which is not what an athlete wants! The reason is because the body produces an "overshoot" of insulin, which helps muscles to take up sugar in the blood. This in turn causes low blood sugar levels.

Athletes should eat foods with a low to medium GI before a match. This allows for a relatively slow release of glucose into the blood and avoids the unwanted insulin surge.

Consuming carbohydrate at least an hour before the start allows any hormonal imbalance to return to normal.

Example low GI foods include pasta, whole grain breads and rice, oatmeal, milk and milk products and fruit (except bananas and dried fruit).

The pre-match meal might consist of pasta in a low-fat tomato sauce, baked beans or scrambled eggs on toast and fresh fruit such as apples, pears or orange juice. Some grilled fish or chicken and vegetables could accompany the carbohydrates. Ideally this meal should be eaten at least three hours prior to the start - especially if nerves are a factor, which can impair digestion.

Food in the stomach is given a high priority to be digested before it has chance to spoil. As a result greater blood flow is directed to the digestive tract - not good news when players' muscles will soon be demanding an increase in blood flow too. The result of performing with a full stomach is nausea - the body's attempt to cease exercise so that it can redirect blood flow back to the stomach.

There is one exception to consuming carbohydrate immediately prior to the start of a game and it's in the form of a sports drink 5 or 10 minutes before kick off. This is discussed in more detail in part 6 tomorrow.

Post Match Eating

As an example, soccer players can use up 200 to 250 grams of carbohydrates during a game. It's important that they (and other athletes that perform for a similar duration) replenish those stores as quickly as possible. It becomes even more important if the athlete has more than one competition in the week or are involved in heavy training.

Ideally, a large, high-carbohydrate meal should be eaten within two hours of the finish and it can and should consist of high GI foods. Bananas and dried fruits are good immediately following a match, as are sandwiches and high-carbohydrate drinks like Gatorade Exceed and Lucozade. A main meal several hours later might consist of bread, pasta, potatoes and rice as well as other simple sugars like cakes and sweets.

Even under the best circumstances it can take over twenty hours to fully restore carbohydrate stores. This has implications for athletes who are competing five or six days a week (perhaps during a tournamnet). In this case carbohydrate replenishment at regular intervals during training sessions becomes very important. This is where high-carbohydrate drinks can offer a real advantage (see Part 6 tomorrow).

Carbohydrate Loading

Carbohydrate loading is often used by long distance athletes to "pack " their muscles with energy. The actual process involves depleting the muscles of carbohydrate a week or so before the event with exhaustive exercise and a low-carbohydrate diet.

Two to three days before the event the athlete switches to a very high-carbohydrate diet. In their depleted state, muscles take up more carbohydrate than they normally would giving the athlete a large store of energy.

For most sports and events, carbohydrate loading is unnecessary. In fact a disruption in an athlete's normal eating pattern can actually cause stomach upset and lead to impaired performance. A more sensible approach is to increase carbohydrate intake in the days leading up to a game or event.

Sports Nutrition Basics

Part 6 - Fluid Replacement & Hydration

Athletes can lose between 2-3 liters of sweat during 90 minutes of intense exercise, particularly in hot and humid conditions. They can also lose as much as 2-3 kg (4-6 lbs) in bodyweight during the same period. This amount of fluid loss will certainly have a negative affect on performance.

Ideally to counteract dehydration, athletes should consume 200-400 ml (7-14 oz) of cold water or a suitable carbohydrate solution 5 to 10 minutes prior to the start of their event. During the any intervals, they should try to drink another 300-500 ml (10-17oz) of a sports drink. During hot weather or strenuous training sessions, coaches should try to provide their athletes with 150-250 ml (5-8oz) of drink about every 20 minutes.

Following a match or hard training session, it's essential that lost fluids be replaced. Water on its own is fine, but to replace fluid AND replenish energy stores, a high carbohydrate drink may be more suitable.

Drinking Before & During Competition

The right carbohydrate drink taken before and during composition can postpone fatigue and stabilize blood sugar preventing light-headedness, headaches, nausea and "jelly-like" muscles. However, not all carbohydrate drinks are created equal. Too much carbohydrate or sugar can actually hinder performance.

A solution that contains 40% carbohydrate empties the stomach much slower than plain water (which is 0% carbohydrate). This means that high sugar drinks such as Coca Cola, regular Lucozade, Exceed High Carbohydrate Source and Gator Lode (up to 40% carbohydrate) are NOT the best fluids to consume before or during exercise.

The ideal sports drink should contain 6-8% carbohydrate. It should also contain a small amount of salt. Sodium concentration in the blood can reduce due to sweating and drinking lots of diluted fluids. If it gets too low it can lead to nausea, headaches and blurred vision. Adding just a pinch of salt can offset this potential danger.

Sodium is also an electrolyte. Electrolytes help control the passage of water between body compartments and they also help to maintain the acid-base balance of the body. Electrolytes (or lack of them) have been associated with muscle cramps in the latter stages of sport games.

Here are some effective sports drinks currently on the market suitable before and during a match or training session:

Suitable Sports Drinks for Sport

Brand Amount of Carbohydrate

Gatorade 6% Lucozade Sport 6.4% Exceed 7.2% Quick Kick 4.7% Isotar NA High Five 6% Powerade 6%

Drink 200-400 ml (7-14oz) of a suitable sports drink 5 to 10 minutes before the start but no earlier unless it's several hours before the start. During any intervals drink up to 300-500 ml (10-17oz). In hot climates try to drink 150-250 (5-8oz) ml every 20 minutes or so.

Drinking After Competition

Within two hours after the event you should aim to consume 100-200 grams of carbohydrate. Muscles are depleted of carbohydrate stores, which need to be replenished as quickly as possible. Sometimes it can be impractical or unpalatable to eat a large meal immediately afterwards. High carbohydrate drinks offer a convenient alternative.

The sports drinks mentioned in the table above are good but this is one of the few occasions when taking a high carbohydrate drink is preferable.

How to Make Your Own Sports Drinks

You may have heard of "isotonic" sports drinks that have been "scientifically developed in conjunction with top athletes". But it's very easy to make your own, low-cost carbohydrate drink that is just as effective!

Isotonic means a fluid containing electrolytes and 6-8% carbohydrate (such as the sports drinks in the table above). To make your own add 200 ml (7oz) of concentrated orange juice (orange squash) to 1 litre (34oz) of water and add a pinch (- teaspoon) of table salt.

Hypotonic is a fluid that contains electrolytes and a very small amount of carbohydrate. This is used in very hot conditions where fluid replacement is the most important factor. To make your own add 100 ml (3.5oz) of concentrated orange juice to 1 litre (34oz) of water and add a pinch (- teaspoon) of table salt.

Hypertonic refers to a fluid that contains a large amount of carbohydrate and is ideal for refuelling after a game. To make your own add 400 ml (13.5oz) of concentrated orange juice to 1 litre (34oz) of water and add a pinch (- teaspoon) of table salt.

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